10. 5G NR Overview and Physical Layer

This text deals primarily with the physical layer. However, to better understand its operation, it is helpful to study its surrounding architecture and protocols. To this end, we first review in this chapter the main architecture options for connection to the core network, followed by the Radio Access Network (RAN) protocol architecture. The RAN is responsible for all radio-related functions, such as coding, modulation, HARQ operation, physical transmission, and scheduling. Following this, we narrow our study within the RAN to the physical layer as specified in 3GPP Release 15, the first 5G release. Here, emphasis is on how physical channels are structured, be they user data or control data conveying, as well as how physical signals are created, such signals being those originating solely in the physical layer. Procedures such as initial access, scheduling, and uplink power and timing control are introduced. How maximum user data rates and low latency are achieved is demonstrated, 5G operating frequency spectrum reviewed, and some typical base station and UE parameters presented. Next, we address certain key features and enhancements introduced in Release 16, Release 17, and Release 18 (5G-Advanced), as well as some planned for Release 19. Finally, relevant 3GPP specifications are listed.